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<h1 id="firstHeading" class="firstHeading"><code>reinterpret_cast</code> conversion</h1>
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<tr class="t-nv-h1"><td colspan="5"> Utilities</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="attributes.html" title="cpp/language/attributes"> Attributes</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Types</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="typedef.html" title="cpp/language/typedef"> <code>typedef</code> declaration</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="type_alias.html" title="cpp/language/type alias"> Type alias declaration</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Casts</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="implicit_cast.html" title="cpp/language/implicit conversion"> Implicit conversions</a> - <a href="explicit_cast.html" title="cpp/language/explicit cast"> Explicit conversions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static_cast.html" title="cpp/language/static cast"><tt>static_cast</tt></a> - <a href="dynamic_cast.html" title="cpp/language/dynamic cast"><tt>dynamic_cast</tt></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="const_cast.html" title="cpp/language/const cast"><tt>const_cast</tt></a> - <strong class="selflink"><tt>reinterpret_cast</tt></strong></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Memory allocation</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="new.html" title="cpp/language/new"> <code>new</code> expression</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="delete.html" title="cpp/language/delete"> <code>delete</code> expression</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> <a href="classes.html" title="cpp/language/classes"> Classes</a></td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="class.html" title="cpp/language/class"> Class declaration</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="initializer_list.html" title="cpp/language/constructor"> Constructors</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="this.html" title="cpp/language/this"> <code>this</code> pointer</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="access.html" title="cpp/language/access"> Access specifiers</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="friend.html" title="cpp/language/friend"> <code>friend</code> specifier</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Class-specific function properties</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="virtual.html" title="cpp/language/virtual"> Virtual function</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="override.html" title="cpp/language/override"> <code>override</code> specifier</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="final.html" title="cpp/language/final"> <code>final</code> specifier</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="explicit.html" title="cpp/language/explicit"><tt>explicit</tt></a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static.html" title="cpp/language/static"><tt>static</tt></a> </td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Special member functions</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="default_constructor.html" title="cpp/language/default constructor"> Default constructor</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="copy_constructor.html" title="cpp/language/copy constructor"> Copy constructor</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="move_constructor.html" title="cpp/language/move constructor"> Move constructor</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="as_operator.html" title="cpp/language/as operator" class="mw-redirect"> Copy assignment</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="move_operator.html" title="cpp/language/move operator" class="mw-redirect"> Move assignment</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="destructor.html" title="cpp/language/destructor"> Destructor</a></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"><a href="templates.html" title="cpp/language/templates"> Templates</a> </td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="class_template.html" title="cpp/language/class template"> Class template </a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="function_template.html" title="cpp/language/function template"> Function template </a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="template_specialization.html" title="cpp/language/template specialization"> Template specialization</a></td></tr>   
<tr class="t-nv"><td colspan="5"> <a href="parameter_pack.html" title="cpp/language/parameter pack"> Parameter packs</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Miscellaneous </td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="asm.html" title="cpp/language/asm"> Inline assembly</a></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="history.html" title="cpp/language/history"> History of C++</a></td></tr>
</table></div></td></tr>
</table></div>
</div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="expressions.html" title="cpp/language/expressions"> Expressions</a><div class="t-navbar-menu"><div><div style="display:inline-block">
<div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h2"><td colspan="5"> General </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="value_category.html" title="cpp/language/value category"> value categories</a> (lvalue, rvalue, xvalue)</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="eval_order.html" title="cpp/language/eval order"> order of evaluation</a> (sequence points)</td></tr>
<tr class="t-nv"><td colspan="5"> <a href="constant_expression.html" title="cpp/language/constant expression"> constant expressions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="expressions.html#Unevaluated_expressions" title="cpp/language/expressions"> unevaluated expressions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="expressions.html#Primary_expressions" title="cpp/language/expressions"> primary expressions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="lambda.html" title="cpp/language/lambda">lambda-expression</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Literals </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="integer_literal.html" title="cpp/language/integer literal">integer literals</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="floating_literal.html" title="cpp/language/floating literal">floating-point literals</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="bool_literal.html" title="cpp/language/bool literal">boolean literals</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="character_literal.html" title="cpp/language/character literal">character literals</a> including <a href="escape.html" title="cpp/language/escape">escape sequences</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="string_literal.html" title="cpp/language/string literal">string literals</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="nullptr.html" title="cpp/language/nullptr">null pointer literal</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="user_literal.html" title="cpp/language/user literal">user-defined literal</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Operators </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_assignment.html" title="cpp/language/operator assignment"> Assignment operators</a>: 
<code>a=b</code>, <code>a+=b</code>, <code>a-=b</code>, <code>a*=b</code>, <code>a/=b</code>, <code>a%=b</code>, <code>a&amp;=b</code>, <code>a|=b</code>, <code>a^=b</code>, <code>a&lt;&lt;=b</code>, <code>a&gt;&gt;=b</code></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_incdec.html" title="cpp/language/operator incdec"> Increment and decrement</a>: <code>++a</code>, <code>--a</code>, <code>a++</code>, <code>a--</code></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_arithmetic.html" title="cpp/language/operator arithmetic"> Arithmetic operators</a>:
<code>+a</code>, <code>-a</code>, <code>a+b</code>, <code>a-b</code>, <code>a*b</code>, <code>a/b</code>, <code>a%b</code>, <code>~a</code>, <code>a&amp;b</code>, <code>a|b</code>, <code>a^b</code>, <code>a&lt;&lt;b</code>, <code>a&gt;&gt;b</code> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_logical.html" title="cpp/language/operator logical"> Logical operators</a>: <code>a||b</code>, <code>a&amp;&amp;b</code>, <code>!a</code></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_comparison.html" title="cpp/language/operator comparison"> Comparison operators</a>: <code>a==b</code>, <code>a!=b</code>, <code>a&lt;b</code>, <code>a&gt;b</code>, <code>a&lt;=b</code>, <code>a&gt;=b</code>, <code>a&lt;=&gt;b</code><span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_member_access.html" title="cpp/language/operator member access"> Member access operators</a>: <code>a[b]</code>, <code>*a</code>, <code>&amp;a</code>, <code>a-&gt;b</code>, <code>a.b</code>, <code>a-&gt;*b</code>, <code>a.*b</code></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_other.html" title="cpp/language/operator other"> Other operators</a>: <code>a(...)</code>, <code>a,b</code>, <code>a?b:c</code> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="new.html" title="cpp/language/new">new-expression</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="delete.html" title="cpp/language/delete">delete-expression</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="throw.html" title="cpp/language/throw">throw-expression</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="alignof.html" title="cpp/language/alignof"><code>alignof</code></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="sizeof.html" title="cpp/language/sizeof"><code>sizeof</code></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="sizeof....html" title="cpp/language/sizeof..."><code>sizeof...</code></a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="typeid.html" title="cpp/language/typeid"><code>typeid</code></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="noexcept.html" title="cpp/language/noexcept"><code>noexcept</code></a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="fold.html" title="cpp/language/fold">Fold expression</a><span class="t-mark-rev t-since-cxx17">(C++17)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_alternative.html" title="cpp/language/operator alternative">Alternative representations of operators</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_precedence.html" title="cpp/language/operator precedence">Precedence and associativity</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operators.html" title="cpp/language/operators">Operator overloading</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="default_comparisons.html" title="cpp/language/default comparisons">Default comparisons</a><span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Conversions </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="implicit_cast.html" title="cpp/language/implicit conversion">Implicit conversions</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="const_cast.html" title="cpp/language/const cast"><code>const_cast</code></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static_cast.html" title="cpp/language/static cast"><code>static_cast</code></a></td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink"><code>reinterpret_cast</code></strong></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="dynamic_cast.html" title="cpp/language/dynamic cast"><code>dynamic_cast</code></a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="explicit_cast.html" title="cpp/language/explicit cast">Explicit conversions</a> <code>(T)a</code>, <code>T(a)</code></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="cast_operator.html" title="cpp/language/cast operator">User-defined conversion</a></td></tr>
</table></div>
</div><div></div></div></div></div><div class="t-navbar-sep"> </div></div>
<p>Converts between types by reinterpreting the underlying bit pattern.
</p>
<h3><span class="mw-headline" id="Syntax">Syntax</span></h3>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td class="t-sdsc-nopad"> <code><b>reinterpret_cast &lt;</b></code> <span class="t-spar">new-type</span> <code><b>&gt; (</b></code> <span class="t-spar">expression</span> <code><b>)</b></code>
</td>
<td class="t-sdsc-nopad">
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<p>Returns a value of type <span class="t-spar">new-type</span>.
</p>
<h3><span class="mw-headline" id="Explanation">Explanation</span></h3>
<p>Unlike <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span></span></span>, but like <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">const_cast</span></span></span>, the <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">reinterpret_cast</span></span></span> expression does not compile to any CPU instructions (except when converting between integers and pointers or on obscure architectures where pointer representation depends on its type). It is purely a compile-time directive which instructs the compiler to treat <span class="t-spar">expression</span> as if it had the type <span class="t-spar">new-type</span>.
</p><p>Only the following conversions can be done with <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">reinterpret_cast</span></span></span>, except when such conversions would cast away <i>constness</i> or <i>volatility</i>.
</p>
<div class="t-li1"><span class="t-li">1)</span> An expression of integral, enumeration, pointer, or pointer-to-member type can be converted to its own type. The resulting value is the same as the value of <span class="t-spar">expression</span>.</div>
<div class="t-li1"><span class="t-li">2)</span> A pointer can be converted to any integral type large enough to hold all values of its type (e.g. to <span class="t-lc"><a href="../types/integer.html" title="cpp/types/integer">std::uintptr_t</a></span>)</div>
<div class="t-li1"><span class="t-li">3)</span> A value of any integral or enumeration type can be converted to a pointer type. A pointer converted to an integer of sufficient size and back to the same pointer type is guaranteed to have its original value, otherwise the resulting pointer cannot be dereferenced safely (the round-trip conversion in the opposite direction is not guaranteed; the same pointer may have multiple integer representations) The null pointer constant <span class="t-lc"><a href="../types/NULL.html" title="cpp/types/NULL">NULL</a></span> or integer zero is not guaranteed to yield the null pointer value of the target type; <a href="static_cast.html" title="cpp/language/static cast"><code>static_cast</code></a> or <a href="implicit_cast.html" title="cpp/language/implicit cast" class="mw-redirect">implicit conversion</a> should be used for this purpose.</div>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<div class="t-li1"><span class="t-li">4)</span> Any value of type <span class="t-lc"><a href="../types/nullptr_t.html" title="cpp/types/nullptr t">std::nullptr_t</a></span>, including <span class="t-c"><span class="mw-geshi cpp source-cpp">nullptr</span></span> can be converted to any integral type as if it were <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">(</span><span class="kw4">void</span><span class="sy2">*</span><span class="br0">)</span><span class="nu0">0</span></span></span>, but no value, not even <span class="t-c"><span class="mw-geshi cpp source-cpp">nullptr</span></span> can be converted to <span class="t-lc"><a href="../types/nullptr_t.html" title="cpp/types/nullptr t">std::nullptr_t</a></span>: <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span></span></span> should be used for that purpose.</div>
</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr>
</table>
<div class="t-li1"><span class="t-li">5)</span> Any object pointer type <code>T1*</code> can be converted to another object pointer type <code><i>cv</i> T2*</code>. This is exactly equivalent to <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span><span class="sy1">&lt;</span></span><i>cv</i><span class="mw-geshi cpp source-cpp"> T2<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="kw1">static_cast</span><span class="sy1">&lt;</span></span><i>cv</i><span class="mw-geshi cpp source-cpp"> <span class="kw4">void</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span></span><span class="t-spar">expression</span><code>))</code></span> (which implies that if <code>T2</code>'s alignment requirement is not stricter than <code>T1</code>'s, the value of the pointer does not change and conversion of the resulting pointer back to its original type yields the original value). In any case, the resulting pointer may only be dereferenced safely if allowed by the <i>type aliasing</i> rules (see below) </div>
<div class="t-li1"><span class="t-li">6)</span> An <span class="t-rev-inl t-until-cxx11"><span><a href="value_category.html#lvalue" title="cpp/language/value category">lvalue</a></span> <span><span class="t-mark-rev t-until-cxx11">(until C++11)</span></span></span><span class="t-rev-inl t-since-cxx11"><span><a href="value_category.html#glvalue" title="cpp/language/value category">glvalue</a></span> <span><span class="t-mark-rev t-since-cxx11">(since C++11)</span></span></span> expression of type <code>T1</code> can be converted to reference to another type <code>T2</code>. The result is that of <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span><span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span>T2<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span>p<span class="br0">)</span></span></span>, where <span class="t-c"><span class="mw-geshi cpp source-cpp">p</span></span> is a pointer of type “pointer to <code>T1</code>” to the object designated by <span class="t-spar">expression</span>. No temporary is created, no copy is made, no constructors or conversion functions are called. The resulting reference can only be accessed safely if allowed by the <i>type aliasing</i> rules (see below)</div>
<div class="t-li1"><span class="t-li">7)</span> Any pointer to function can be converted to a pointer to a different function type. Calling the function through a pointer to a different function type is undefined, but converting such pointer back to pointer to the original function type yields the pointer to the original function.</div>
<div class="t-li1"><span class="t-li">8)</span> On some implementations (in particular, on any POSIX compatible system as required by <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/dlsym.html"><code>dlsym</code></a>), a function pointer can be converted to <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span><span class="sy2">*</span></span></span> or any other object pointer, or vice versa. If the implementation supports conversion in both directions, conversion to the original type yields the original value, otherwise the resulting pointer cannot be dereferenced or called safely. </div>
<div class="t-li1"><span class="t-li">9)</span> The null pointer value of any pointer type can be converted to any other pointer type, resulting in the null pointer value of that type. Note that the null pointer constant <span class="t-c"><span class="mw-geshi cpp source-cpp">nullptr</span></span> or any other value of type <span class="t-lc"><a href="../types/nullptr_t.html" title="cpp/types/nullptr t">std::nullptr_t</a></span> cannot be converted to a pointer with <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">reinterpret_cast</span></span></span>: implicit conversion or <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span></span></span> should be used for this purpose.</div>
<div class="t-li1"><span class="t-li">10)</span> A pointer to member function can be converted to pointer to a different member function of a different type. Conversion back to the original type yields the original value, otherwise the resulting pointer cannot be used safely.</div>
<div class="t-li1"><span class="t-li">11)</span> A pointer to member object of some class <code>T1</code> can be converted to a pointer to another member object of another class <code>T2</code>. If <code>T2</code>'s alignment is not stricter than <code>T1</code>'s, conversion back to the original type <code>T1</code> yields the original value, otherwise the resulting pointer cannot be used safely.</div>
<p>As with all cast expressions, the result is:
</p>
 <table class="t-rev-begin">
<tr class="t-rev t-until-cxx11"><td>
<ul><li> an lvalue if <span class="t-spar">new-type</span> is a reference type;
</li><li> an rvalue otherwise.
</li></ul>
</td>
<td><span class="t-mark-rev t-until-cxx11">(until C++11)</span></td></tr>
<tr class="t-rev t-since-cxx11"><td>
<ul><li> an lvalue if <span class="t-spar">new-type</span> is an lvalue reference type or an rvalue reference to function type;
</li><li> an xvalue if <span class="t-spar">new-type</span> is an rvalue reference to object type; 
</li><li> a prvalue otherwise.
</li></ul>
</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr>
</table>
<h3><span class="mw-headline" id="Keywords">Keywords</span></h3>
<p><a href="../keyword/reinterpret_cast.html" title="cpp/keyword/reinterpret cast"><tt>reinterpret_cast</tt></a>
</p>
<h3><span class="mw-headline" id="Type_aliasing"> Type aliasing </span></h3>
<p>Whenever an attempt is made to read or modify the stored value of an object of type <code>DynamicType</code> through a glvalue of type <code>AliasedType</code>, the behavior is undefined unless one of the following is true:
</p>
<ul><li> <code>AliasedType</code> and <code>DynamicType</code> are <i>similar</i>.
</li><li> <code>AliasedType</code> is the (possibly <a href="cv.html" title="cpp/language/cv">cv</a>-qualified) signed or unsigned variant of <code>DynamicType</code>.
</li><li> <code>AliasedType</code> is <span class="t-rev-inl t-since-cxx17"><span><a href="../types/byte.html" title="cpp/types/byte"><tt>std::byte</tt></a>,</span> <span><span class="t-mark-rev t-since-cxx17">(since C++17)</span></span></span> <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span></span></span>, or <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">char</span></span></span>: this permits examination of the  <a href="objects.html#Object_representation_and_value_representation" title="cpp/language/object">object representation</a> of any object as an array of bytes.
</li></ul>
<p>Informally, two types are <i>similar</i> if, ignoring top-level cv-qualification:
</p>
<ul><li> they are the same type; or
</li><li> they are both pointers, and the pointed-to types are similar; or
</li><li> they are both pointers to member of the same class, and the types of the pointed-to members are similar; or
</li></ul>
 <table class="t-rev-begin">
<tr class="t-rev t-until-cxx20"><td>
<ul><li> they are both arrays of the same size or both arrays of unknown bound, and the array element types are similar.
</li></ul>
</td>
<td><span class="t-mark-rev t-until-cxx20">(until C++20)</span></td></tr>
<tr class="t-rev t-since-cxx20"><td>
<ul><li> they are both arrays of the same size or at least one of them is array of unknown bound, and the array element types are similar.
</li></ul>
</td>
<td><span class="t-mark-rev t-since-cxx20">(since C++20)</span></td></tr>
</table>
<p>For example:
</p>
<ul><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <span class="kw4">int</span> <span class="sy2">*</span> <span class="kw4">volatile</span> <span class="sy2">*</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="sy2">*</span> <span class="sy2">*</span> <span class="kw4">const</span></span></span> are similar;
</li><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span> <span class="kw4">volatile</span> S<span class="sy4">::</span><span class="sy2">*</span> <span class="kw4">const</span><span class="br0">)</span><span class="br0">[</span><span class="nu0">20</span><span class="br0">]</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span> <span class="kw4">const</span> S<span class="sy4">::</span><span class="sy2">*</span> <span class="kw4">volatile</span><span class="br0">)</span><span class="br0">[</span><span class="nu0">20</span><span class="br0">]</span></span></span> are similar;
</li><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span> <span class="kw4">const</span> <span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> <span class="sy2">*</span><span class="br0">)</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span> <span class="kw4">volatile</span> <span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> <span class="sy2">*</span><span class="br0">)</span></span></span> are similar;
</li><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span>S<span class="sy4">::</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span>S<span class="sy4">::</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="br0">)</span></span></span> are <i>not</i> similar;
</li><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> <span class="sy2">*</span><span class="br0">)</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> <span class="kw4">int</span> <span class="sy2">*</span><span class="br0">)</span></span></span> are <i>not</i> similar;
</li><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">const</span> <span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> <span class="sy2">*</span><span class="br0">)</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> <span class="sy2">*</span><span class="br0">)</span></span></span> are <i>not</i> similar;
</li><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> <span class="sy2">*</span> <span class="kw4">const</span><span class="br0">)</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span> <span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">int</span> <span class="sy2">*</span><span class="br0">)</span></span></span> are similar (they are the same type);
</li><li><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="../utility/pair.html"><span class="kw1099">std::<span class="me2">pair</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>, <span class="kw4">int</span><span class="sy1">&gt;</span></span></span> and <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="../utility/pair.html"><span class="kw1099">std::<span class="me2">pair</span></span></a><span class="sy1">&lt;</span><span class="kw4">const</span> <span class="kw4">int</span>, <span class="kw4">int</span><span class="sy1">&gt;</span></span></span> are <i>not</i> similar.
</li></ul>
<p>This rule enables type-based alias analysis, in which a compiler assumes that the value read through a glvalue of one type is not modified by a write to a glvalue of a different type (subject to the exceptions noted above).
</p><p>Note that many C++ compilers relax this rule, as a non-standard language extension, to allow wrong-type access through the inactive member of a <a href="union.html" title="cpp/language/union">union</a> (such access is not undefined in C).
</p>
<h3><span class="mw-headline" id="Notes">Notes</span></h3>
<p>Assuming that alignment requirements are met, a <code>reinterpret_cast</code> does not change the <a href="pointer.html#Pointers" title="cpp/language/pointer">value of a pointer</a> outside of a few limited cases dealing with <a href="static_cast.html#pointer-interconvertible" title="cpp/language/static cast"><i>pointer-interconvertible</i></a> objects:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">struct</span> S1 <span class="br0">{</span> <span class="kw4">int</span> a<span class="sy4">;</span> <span class="br0">}</span> s1<span class="sy4">;</span>
<span class="kw1">struct</span> S2 <span class="br0">{</span> <span class="kw4">int</span> a<span class="sy4">;</span> <span class="kw1">private</span><span class="sy4">:</span> <span class="kw4">int</span> b<span class="sy4">;</span> <span class="br0">}</span> s2<span class="sy4">;</span> <span class="co1">// not standard-layout</span>
<span class="kw1">union</span> U <span class="br0">{</span> <span class="kw4">int</span> a<span class="sy4">;</span> <span class="kw4">double</span> b<span class="sy4">;</span> <span class="br0">}</span> u <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">0</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">int</span> arr<span class="br0">[</span><span class="nu0">2</span><span class="br0">]</span><span class="sy4">;</span>
 
<span class="kw4">int</span><span class="sy2">*</span> p1 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>s1<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// value of p1 is "pointer to s1.a" because</span>
                                       <span class="co1">// s1.a and s1 are pointer-interconvertible</span>
 
<span class="kw4">int</span><span class="sy2">*</span> p2 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>s2<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// value of p2 is unchanged by reinterpret_cast</span>
                                       <span class="co1">// and is "pointer to s2". </span>
 
<span class="kw4">int</span><span class="sy2">*</span> p3 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>u<span class="br0">)</span><span class="sy4">;</span>  <span class="co1">// value of p3 is "pointer to u.a":</span>
                                       <span class="co1">// u.a and u are pointer-interconvertible</span>
 
<span class="kw4">double</span><span class="sy2">*</span> p4 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">double</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span>p3<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// value of p4 is "pointer to u.b": u.a and</span>
                                            <span class="co1">// u.b are pointer-interconvertible because</span>
                                            <span class="co1">// both are pointer-interconvertible with u</span>
 
<span class="kw4">int</span><span class="sy2">*</span> p5 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>arr<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// value of p5 is unchanged by reinterpret_cast</span>
                                        <span class="co1">// and is "pointer to arr"</span></pre></div></div>
<p>Performing a class member access that designates a non-static data member or a non-static member function on a glvalue that does not actually designate an object of the appropriate type - such as one obtained through a <code>reinterpret_cast</code> - results in undefined behavior:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw1">struct</span> S <span class="br0">{</span> <span class="kw4">int</span> x<span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">struct</span> T <span class="br0">{</span> <span class="kw4">int</span> x<span class="sy4">;</span> <span class="kw4">int</span> f<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">struct</span> S1 <span class="sy4">:</span> S <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>    <span class="co1">// standard-layout</span>
<span class="kw1">struct</span> ST <span class="sy4">:</span> S, T <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span> <span class="co1">// not standard-layout</span>
 
S s <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">auto</span> p <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span>T<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>s<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// value of p is "pointer to s"</span>
<span class="kw4">auto</span> i <span class="sy1">=</span> p<span class="sy2">-</span><span class="sy1">&gt;</span>x<span class="sy4">;</span> <span class="co1">// class member access expression is undefined behavior;</span>
               <span class="co1">// s is not a T object</span>
p<span class="sy2">-</span><span class="sy1">&gt;</span>x <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span> <span class="co1">// undefined behavior</span>
p<span class="sy2">-</span><span class="sy1">&gt;</span>f<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>   <span class="co1">// undefined behavior</span>
 
S1 s1 <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">auto</span> p1 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span>S<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>s1<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// value of p1 is "pointer to the S subobject of s1"</span>
<span class="kw4">auto</span> i <span class="sy1">=</span> p1<span class="sy2">-</span><span class="sy1">&gt;</span>x<span class="sy4">;</span> <span class="co1">// OK</span>
p1<span class="sy2">-</span><span class="sy1">&gt;</span>x <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span>      <span class="co1">// OK</span>
 
ST st <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
<span class="kw4">auto</span> p2 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span>S<span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>st<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// value of p2 is "pointer to st"</span>
<span class="kw4">auto</span> i <span class="sy1">=</span> p2<span class="sy2">-</span><span class="sy1">&gt;</span>x<span class="sy4">;</span> <span class="co1">// undefined behavior</span>
p2<span class="sy2">-</span><span class="sy1">&gt;</span>x <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span>      <span class="co1">// undefined behavior</span></pre></div></div>
<p>Many compilers issue "strict aliasing" warnings in such cases, even though technically such constructs run afoul of something other than the paragraph commonly known as the "strict aliasing rule".
</p><p>The purpose of strict aliasing and related rules is to enable type-based alias analysis, which would be decimated if a program can validly create a situation where two pointers to unrelated types (e.g., an <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">int</span><span class="sy2">*</span></span></span> and a <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">float</span><span class="sy2">*</span></span></span>) could simultaneously exist and both can be used to load or store the same memory (see <a rel="nofollow" class="external text" href="http://www.open-std.org/pipermail/ub/2016-February/000565.html">this email on SG12 reflector</a>). Thus, any technique that is seemingly capable of creating such a situation necessarily invokes undefined behavior.
</p><p>When it is needed to interpret the bytes of an object as a value of a different type, <span class="t-lc"><a href="../string/byte/memcpy.html" title="cpp/string/byte/memcpy">std::memcpy</a></span> <span class="t-rev-inl t-since-cxx20"><span>or <a href="../numeric/bit_cast.html" title="cpp/numeric/bit cast"><tt>std::bit_cast</tt></a> </span> <span><span class="t-mark-rev t-since-cxx20">(since C++20)</span></span></span>can be used:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw4">double</span> d <span class="sy1">=</span> <span class="nu16">0.1</span><span class="sy4">;</span>
<a href="../types/integer.html"><span class="kw115">std::<span class="me2">int64_t</span></span></a> n<span class="sy4">;</span>
static_assert<span class="br0">(</span>sizeof n <span class="sy1">==</span> sizeof d<span class="br0">)</span><span class="sy4">;</span>
<span class="co1">// n = *reinterpret_cast&lt;std::int64_t*&gt;(&amp;d); // Undefined behavior</span>
<a href="../string/byte/memcpy.html"><span class="kw1162">std::<span class="me2">memcpy</span></span></a><span class="br0">(</span><span class="sy3">&amp;</span>n, <span class="sy3">&amp;</span>d, sizeof d<span class="br0">)</span><span class="sy4">;</span>               <span class="co1">// OK</span>
n <span class="sy1">=</span> <a href="../numeric/bit_cast.html"><span class="kw2690">std::<span class="me2">bit_cast</span></span></a><span class="sy1">&lt;</span><a href="../types/integer.html"><span class="kw115">std::<span class="me2">int64_t</span></span></a><span class="sy1">&gt;</span><span class="br0">(</span>d<span class="br0">)</span><span class="sy4">;</span>          <span class="co1">// also OK</span></pre></div></div>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<p>If the implementation provides <span class="t-lc"><a href="../types/integer.html" title="cpp/types/integer">std::intptr_t</a></span> and/or <span class="t-lc"><a href="../types/integer.html" title="cpp/types/integer">std::uintptr_t</a></span>, then a cast from a pointer to an object type or <i>cv</i> <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span> to these types is always well-defined. However, this is not guaranteed for a function pointer.
</p>
</td>
<td><span class="t-mark-rev t-since-cxx11">(since C++11)</span></td></tr>
</table>
<p>The paragraph defining the strict aliasing rule in the standard used to contain two additional bullets partially inherited from C:
</p>
<ul><li> <code>AliasedType</code> is an <a href="aggregate_initialization.html" title="cpp/language/aggregate initialization">aggregate type</a> or a <a href="union.html" title="cpp/language/union">union</a> type which holds one of the aforementioned types as an element or non-static member (including, recursively, elements of subaggregates and non-static data members of the contained unions).
</li><li> <code>AliasedType</code> is a (possibly <a href="cv.html" title="cpp/language/cv">cv</a>-qualified) <a href="derived_class.html" title="cpp/language/derived class">base class</a> of <code>DynamicType</code>.
</li></ul>
<p>These bullets describe situations that cannot arise in C++ and therefore are omitted from the discussion above. In C, aggregate copy and assignment access the aggregate object as a whole. But in C++ such actions are always performed through a member function call, which accesses the individual subobjects rather than the entire object (or, in the case of unions, copies the object representation, i.e., via <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">unsigned</span> <span class="kw4">char</span></span></span>). These bullets were eventually removed via <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/2051.html">CWG2051</a>.
</p>
<h3><span class="mw-headline" id="Example">Example</span></h3>
<div class="t-example"><p>Demonstrates some uses of <code>reinterpret_cast</code>:</p><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;cstdint&gt;</span>
<span class="co2">#include &lt;cassert&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
 
<span class="kw4">int</span> f<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="nu0">42</span><span class="sy4">;</span> <span class="br0">}</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw4">int</span> i <span class="sy1">=</span> <span class="nu0">7</span><span class="sy4">;</span>
 
    <span class="co1">// pointer to integer and back</span>
    <a href="../types/integer.html"><span class="kw139">std::<span class="me2">uintptr_t</span></span></a> v1 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><a href="../types/integer.html"><span class="kw139">std::<span class="me2">uintptr_t</span></span></a><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>i<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// static_cast is an error</span>
    <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"The value of &amp;i is "</span> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/showbase.html"><span class="kw1770">std::<span class="me2">showbase</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/hex.html"><span class="kw1786">std::<span class="me2">hex</span></span></a> <span class="sy1">&lt;&lt;</span> v1 <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
    <span class="kw4">int</span><span class="sy2">*</span> p1 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span>v1<span class="br0">)</span><span class="sy4">;</span>
    <a href="../error/assert.html"><span class="kw775">assert</span></a><span class="br0">(</span>p1 <span class="sy1">==</span> <span class="sy3">&amp;</span>i<span class="br0">)</span><span class="sy4">;</span>
 
    <span class="co1">// pointer to function to another and back</span>
    <span class="kw4">void</span><span class="br0">(</span><span class="sy2">*</span>fp1<span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">void</span><span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="br0">)</span><span class="sy1">&gt;</span><span class="br0">(</span>f<span class="br0">)</span><span class="sy4">;</span>
    <span class="co1">// fp1(); undefined behavior</span>
    <span class="kw4">int</span><span class="br0">(</span><span class="sy2">*</span>fp2<span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span><span class="br0">)</span><span class="sy1">&gt;</span><span class="br0">(</span>fp1<span class="br0">)</span><span class="sy4">;</span>
    <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/hex.html"><span class="kw1785">std::<span class="me2">dec</span></span></a> <span class="sy1">&lt;&lt;</span> fp2<span class="br0">(</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// safe</span>
 
    <span class="co1">// type aliasing through pointer</span>
    <span class="kw4">char</span><span class="sy2">*</span> p2 <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">char</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy3">&amp;</span>i<span class="br0">)</span><span class="sy4">;</span>
    <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="br0">(</span>p2<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span> <span class="sy1">==</span> <span class="st0">'\x7'</span> <span class="sy4">?</span> <span class="st0">"This system is little-endian<span class="es1">\n</span>"</span>
                                 <span class="sy4">:</span> <span class="st0">"This system is big-endian<span class="es1">\n</span>"</span><span class="br0">)</span><span class="sy4">;</span>
 
    <span class="co1">// type aliasing through reference</span>
    <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">unsigned</span> <span class="kw4">int</span><span class="sy3">&amp;</span><span class="sy1">&gt;</span><span class="br0">(</span>i<span class="br0">)</span> <span class="sy1">=</span> <span class="nu0">42</span><span class="sy4">;</span>
    <a href="../io/cout.html"><span class="kw1762">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> i <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
 
    <span class="br0">[</span><span class="br0">[</span>maybe_unused<span class="br0">]</span><span class="br0">]</span> <span class="kw4">const</span> <span class="kw4">int</span> <span class="sy3">&amp;</span>const_iref <span class="sy1">=</span> i<span class="sy4">;</span>
    <span class="co1">// int &amp;iref = reinterpret_cast&lt;int&amp;&gt;(</span>
    <span class="co1">//     const_iref); // compiler error - can't get rid of const</span>
    <span class="co1">// Must use const_cast instead: int &amp;iref = const_cast&lt;int&amp;&gt;(const_iref);</span>
<span class="br0">}</span></pre></div></div>
<p>Possible output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">The value of &amp;i is 0x7fff352c3580
42
This system is little-endian
42</pre></div></div> 
</div>
<h3><span class="mw-headline" id="Defect_reports"> Defect reports </span></h3>
<p>The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
</p>
<table class="dsctable" style="font-size:0.8em">
<tr>
<th> DR
</th>
<th> Applied to
</th>
<th> Behavior as published
</th>
<th> Correct behavior
</th></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/195.html">CWG 195</a>
</td>
<td> C++98
</td>
<td> conversion between function pointers<br>and object pointers not allowed
</td>
<td> made conditionally-supported
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/658.html">CWG 658</a>
</td>
<td> C++98
</td>
<td> the result of pointer conversions was unspecified<br>(except for conversions back to the original type)
</td>
<td> specification provided for pointers<br>whose pointed-to types satisfy<br>the alignment requirements
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/799.html">CWG 799</a>
</td>
<td> C++98
</td>
<td> it was unclear which identity conversion<br>can be done by <code>reinterpret_cast</code>
</td>
<td> made clear
</td></tr>
<tr>
<td> <a rel="nofollow" class="external text" href="https://cplusplus.github.io/CWG/issues/1268.html">CWG 1268</a>
</td>
<td> C++11
</td>
<td> <code>reinterpret_cast</code> could only cast lvalues to reference types
</td>
<td> xvalues also allowed
</td></tr></table>
<h3><span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <a href="const_cast.html" title="cpp/language/const cast"> <code>const_cast</code> conversion </a>
</td>
<td>  adds or removes const</td></tr>

<tr class="t-dsc">
<td>  <a href="static_cast.html" title="cpp/language/static cast"> <code>static_cast</code> conversion </a>
</td>
<td>  performs basic conversions</td></tr>

<tr class="t-dsc">
<td>  <a href="dynamic_cast.html" title="cpp/language/dynamic cast"> <code>dynamic_cast</code> conversion </a>
</td>
<td>  performs checked polymorphic conversions</td></tr>

<tr class="t-dsc">
<td>  <a href="explicit_cast.html" title="cpp/language/explicit cast"> explicit casts </a>
</td>
<td>  permissive conversions between types </td></tr>

<tr class="t-dsc">
<td>  <a href="implicit_cast.html" title="cpp/language/implicit cast" class="mw-redirect"> standard conversions </a>
</td>
<td>  implicit conversions from one type to another</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="../numeric/bit_cast.html" title="cpp/numeric/bit cast"> <span class="t-lines"><span>bit_cast</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div></div>
</td>
<td>   reinterpret the object representation of one type as that of another  <br> <span class="t-mark">(function template)</span> </td></tr>
</table>

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